Delta1 Gruis

Delta¹ Gruis, Latinized from δ¹ Gruis, is a candidate binary star^[10] system in the constellation Grus. With a peak apparent visual magnitude of 4.0 it is bright enough to be seen with the naked eye at night. The distance to this system, as determined using an annual parallax shift of 10.54 mas as seen from the Earth,^[1] is around 309 light years. It is gradually moving away from the Sun with a radial velocity of +4.9 km/s.^[5]

For other stars with this Bayer designation, see δ Gruis.

δ¹ Gruis

Location of δ1 Gruis (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Grus
Right ascension	22h 29m 16.17481s[1]
Declination	−43° 29′ 44.0245″[1]
Apparent magnitude (V)	4.0 - 4.2[2]
Characteristics
Spectral type	G6/8 III[3]
U−B color index	+0.81[4]
B−V color index	+1.03[4]
Variable type	SR[2]
Astrometry
Radial velocity (Rv)	+4.9±0.8[5] km/s
Proper motion (μ)	RA: +25.72[1] mas/yr Dec.: −3.32[1] mas/yr
Parallax (π)	10.54±0.22 mas[1]
Distance	309 ± 6 ly (95 ± 2 pc)
Absolute magnitude (MV)	−1.1[6]
Details
Mass	4.0[6] M☉
Radius	24[6] R☉
Luminosity	305[6] L☉
Surface gravity (log g)	2.54±0.28[7] cgs
Temperature	5,013±88[7] K
Metallicity [Fe/H]	−0.23±0.09[7] dex
Rotational velocity (v sin i)	8.2[8] km/s
Other designations
δ1 Gru, CD−44°14931, FK5 846, HD 213009, HIP 110997, HR 8556, SAO 231154, WDS J22293-4330A[9]
Database references
SIMBAD	data

The brighter component of this system is an evolved, yellow-hued, G-type giant star with a stellar classification of G6/8 III.^[3] It is a semiregular variable that ranges between apparent magnitudes 3.99 and 4.2,^[2] located 325 light-years from Earth. Delta¹ Gruis has around 3 times the mass and 24 times the diameter of the Sun. The fainter companion is a magnitude 12.8 star at an angular separation of 5.6 arc seconds, as of 2008.^[10]

See also

• List of stars in Grus